Power MOSFETs for Isolated DC-to-DC Converters

A new series of LITTLE FOOT&reg MOSFETs aimed at isolated dc-to-dc converters powered by a 24-V or 48-V bus was announced by Siliconix incorporated, an 80.4%-owned subsidiary of Vishay Intertechnology, Inc.

Intended for use in a wide range of telecommunications, high-voltage computer and server, and automotive products, the seven new n-channel devices are offered in breakdown voltages ranging from 60 V to 200 V.

The Vishay Siliconix Si4850EY (60 V), Si4896DY (80 V), Si4484EY (100 V), Si4848DY (150 V), and Si4490DY (200 V) are designed for use on the primary side of dc-to-dc converters requiring higher frequencies or lower switching losses, and feature typical gate charge ratings from 18 nC to 34 nC in combination with on-resistance values ranging from 16.5 mW to 100 mW at a 10-V gate drive.

The product of on-resistance times gate charge-a key figure of merit for power conversion applications-has been improved by 34% or more for each of the breakdown voltages provided by the new products, setting new industry records. With their optimized on-resistance and gate charge ratings, the new devices open the door to higher-frequency converters and smaller filtering components, or to cooler-running circuits enabled by lower switching and conduction losses.

Whether the objective is to generate less heat, or to minimize the size of end products with higher-frequency dc-to-dc converters, these new LITTLE FOOT devices represent a significant improvement over the power MOSFETs that have been available until now for medium-voltage systems. And with voltage ratings from 200 V down to 60 V, designers can have maximum flexibility in choosing the right topology for their applications.